As a solid-state imaging device, for example, a CMOS image sensor is known. The CMOS image sensor amplifies a pixel signal detected by a photodiode for each cell configuring one pixel by means of a transistor. In the CMOS image sensor, a dynamic shift register is used as a circuit that horizontally or vertically scans an imaging unit having pixels arranged in a two-dimensional form and an attempt is made to simplify and miniaturize the circuit and reduce the power consumption thereof.
With miniaturization of the CMOS image sensor, the pixel is further miniaturized. A method for performing an ion-implanting process in a self-alignment manner after a gate electrode of a transfer transistor is formed in order to precisely form an N-type region and P-type region that configures a photodiode with respect to the transfer transistor when the pixels are miniaturized.
Since impurity ions are implanted into a semiconductor substrate with high acceleration energy (for example, 150 keV or more) when impurity ions are implanted in a self-alignment manner with respect to the gate electrode to form the N-type region of the photodiode, the impurity ions penetrate through the gate electrode formed of polysilicon to reach the semiconductor substrate. In order to prevent the impurity ions from reaching the semiconductor substrate lying directly under the gate electrode, it is necessary to form a cap member on the gate electrode and prevent the impurity ions from penetrating through the gate electrode. However, since a cap member is not required when logic transistors are formed in a surrounding portion of the pixel, a cap member is required only for the transistor configuring the pixel. As a result, the manufacturing process becomes complicated and the cost of the CMOS image sensor is raised.